Publication Date

Spring 2021

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Climate Science

Advisor

Alison F. Bridger

Keywords

Dust, Mars, Modeling, Pluming, Radiative Heating, Saltation

Subject Areas

Atmospheric sciences; Planetology; Remote sensing

Abstract

The annually-recurring, regional B storm on Mars occurs at the highest southernlatitudes in years lacking a global dust storm (GDS), and produces warm temperatures (> 200 K) at 50 Pa over the south pole. Observations of the B storm are limited due to the lack of in-situ data in the polar regions of Mars, and reproducing polar phenomena using traditional latitude-longitude grid models is difficult because of the increasingly small grid spacing at the poles. The development of the new NASA Ames Mars Global Climate Model (MGCM), which has a finite-volume dynamical core, a uniform cubed-sphere grid, and several of the physics schemes from the NASA Ames Legacy MGCM, provides an opportunity to simulate the B storm at high resolution on a uniform polar grid. This thesis characterizes the evolution of the annually recurring, regional B storm on Mars using MGS/TES and MRO/MCS observations of temperature and dust retrieved from orbit during seven non-GDS Mars Years (MY24, MY26, and MY29–MY34). We define and describe the growth (Ls = 247°–257°), peak (Ls = 267°), and decay (Ls = 277°–287°) phases of the B storm using these observed fields, and then use our analysis to reproduce the storm with the MGCM. We find that the model predicts that dust plumes develop in the eastern hemisphere during the B storm, and that the ascending dust pattern resembles the solar escalator effect. The pluming is well-defined for ~5° of Ls around peak intensity (Ls = 267°) and lofts the dust as high as 5 Pa. The model predicts that dust lifting occurs along the receding CO2 cap edge during the B storm. Model-predicted surface stresses exceed both the fluid and impact thresholds for the saltation of sand-size particles in various regions around the simulated CO2 cap edge during the simulated B storm.

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